| 摘要 |
713,140. Thermionic cathode constructions. PHILIPS ELECTRICAL INDUSTRIES, Ltd. July 17, 1952 [July 20, 1951], No. 18101/52. Class 39(1) [Also in Group XXII] A method of manufacturing dispenser cathodes consists in moulding and presintering a porous body of refractory metal to form the wall 4 of the cathode, sleeving the body over a part of the cathode which has a higher coefficient of thermal expansion, to form the cavity and heating the cathode above its operating temperature and at least 200‹C higher than the pre-sintering temperature. In a cathode for magnetrons, a molybdenum body 1 contains barium-strontium carbonates 3, (which decompose to oxides during heating), in a chamber sealed by the porous tungsten tube 4. The tube is moulded from powder of sizes 1.5Á to 6.1Á and above at 2,000 kg/sq. cm. The tube is then pre-sintered at 900-1000‹C and sintered at 1300-1800‹C. A modified tungsten tube 8, Fig. 2, may be used. The sintering may take place in a helium, argon or nitrogen-hydrogen atmosphere. The pre-sintered tube may be machined to size before being slipped over the structure. Specification 705,537 is referred to. |
